The inevitable depletion of fossil fuel reserves and the subsequent hike in fuel price along with the environmental concerns of conventional fuels has drawn much attention of researchers to develop an industrially and environmentally benign process for production of biofuels and biofuel additives from the renewable resources. Recently, butyl acetate bearing high flash point (22 C) and very low freezing point (−73 C) has been recognized as a potential biofuel additive. Low freezing point (−73 C) of butyl acetate improves the cold flow properties of biodiesel without significantly affecting cetane number and the mixture's heat of combustion. Moreover, its high flash point (22 C) makes it safer to use as biodiesel additive and it also makes superior than the ethyl acetate with flash point of −4 C and similar other biodiesel additives.
Butyl acetate is widely used in pharmaceutical, paint, high-grade paints, inks, resins and acetic acid and solvent dehydration, but also can replace MTBE, a gasoline additive, is a remarkably versatile fine chemicals. Also, butyl acetate holds great potential as a sustainable biofuel additive. Butyl acetate is an important solvent for plastics, resins, gums, and coatings. Butyl acetate can also be used as an extracting agent, as an intermediate in organic synthesis, or in the photographic industry. The traditional production of butyl acetate from acetic acid involves use of butanol as raw materials and sulfuric acid as a catalyst esterification. The disadvantage of this process is existence of serious equipment corrosion, environmental pollution, etc.
Heterogeneously catalyzed transesterification of biobutanol and bioethylacetate can produce butyl acetate. This route is economical, eco-friendly and offers several advantages over the commonly used Fischer Esterification, refer Fischer, E., Speier, A., 1895. Darstellung der Ester. Chemische Berichte 28, 3252-3258. Bio butanol can be made from fermentation of lignocellulosic biomass and bio ethyl acetate through economical renewable ways. Thus transesterification or acetylation of bio ethyl acetate with bio butanol is a sustainable option for renewable butyl acetate production. The co product formed is ethanol which undergoes esterification once again to form ethyl acetate and gets recycled for acetylation. Further, this route does not require special grade (acetic acid resistant) stainless steel equipments and is devoid of serious contamination (associated with the use of homogeneous catalysts) and waste water (formed as product) disposal problems. But, generally, acetylation reaction is slow and is catalyzed by heterogeneous ion exchange resins.
Another route of synthesis of butyl acetate that is well established is the esterification of acetic acid with butanol, but this needs special reactors that are resistant to acetic acid and water is produced as by-product which is wasted.
Article titled “Potential biofuel additive from renewable sources—Kinetic study of formation of butyl acetate by heterogeneously catalyzed transesterification of ethyl acetate with butanol” by S H Ali et al. published in Bioresource Technology, 2011, 102 (21), pp 10094-10103 reports heterogeneously catalyzed transesterification of biobutanol and bioethylacetate to produce butyl acetate. The Amberlite IR 120- and Amberlyst 15 catalyzed transesterification was studied in a batch reactor over a range of catalyst loading (6-12 wt. %), alcohol to ester feed ratio (1:3 to 3:1), and temperature (303.15-333.15 K). This article reports the conversion of butanol up to 75%.
Article titled “Transesterification of Esters such as Ethyl Acetate with Alcohols over Mordenite Type of Zeolite H-Z-HM15” by H Ogava published in Bulletin of Tokyo Gakugei University Sect. IV, 2004, 56, pp. 53-56 reports use of Mordenite type of zeolite H-Z-HM15 catalyst for the transesterification of esters such as ethyl acetate with alcohols. The article reports H-Z-HM15 is the effective catalyst for transesterification of aliphatic acetate such as ethyl acetate and alcohols such as n-butanol and showed its shape selective property for the reaction.
Article titled “Catalytic performances of heteropoly compounds supported on dealuminated ultra-stable Y zeolite for liquid-phase esterification” by F Zhang et al. published in Science in China Series B, 2006, 49 (2), pp 140-147 reports A series of catalysts of 12-Phosphotungstic acid (PW) and its cesium salts immobilized on dealuminated ultra-stable Y zeolite (DUSY). The catalytic activity was improved remarkably by introducing PW onto dealuminated USY (from 49.5% to 86.4%). The supported cesium salt of PW on DUSY catalyst gave a very high conversion of n-butanol of 94.6% and the 100% selectivity for n-butyl acetate.
Chinese patent application no. 1301152 discloses a dealuminated ultra stable Y zeolite catalyst preparation method, Salts miscellaneous loading and its application in the liquid phase esterification reactions. The catalyst is used in the esterification of acetic acid and n-butanol liquid phase reaction, having a low reaction temperature, high conversion rate.
Article titled “Catalytic application of hydrophobic properties of high-silica zeolites ii. esterification of acetic acid with butanols” by S Namba et al. published in Studies in Surface Science and Catalysis, 1985, Volume 20, Pages 205-211 reports liquid-phase esterification of acetic acid with n-, i- or t-butanol on high-silica zeolites. Although, the non-dealuminated HY zeolite was hardly active for the esterification, the dealuminated HY and HZSM-5 zeolites were active and their activities changed with their Si/Al ratios.
Article titled “Catalytic studies of Boron-HZSM-5 zeolite for methane conversion to higher hydrocarbons” by R Mat et al. published in Journal of Chemical and Natural Resources Engineering, Special edition, 2008, pp 146-152 reports the modification of HZSM-5 catalyst with boron in order to reduce the acidity of the catalyst and thus reduce it oxidation activity. A series of boron was loaded into HZSM-5 zeolite via impregnation. Boron oxide covered the active site of HZSM-5 which were responsible for activation of methane thus resulted in lower methane conversion at higher boron loading.
Article titled “Biodiesel production via ethylic transesterification with basic zeolites” by G Ghesti et al. published in Quim. Nova, 2012, Vol. 35, No. 1, pp 119-123 reports Soybean oil transesterification with ethanol in a batch reactor using USY zeolites modified with barium and strontium (15 wt. %) as catalysts. The Ba/USY provided higher conversions (>97%) than Sr/USY (<75%). The increased in catalytic activity of Ba/USY was attributed to two different effects: a larger number of basic sites; and a lower interaction between barium species and HUSY Bronsted sites.
A review article titled “An overview on synthetic methods of n-butyl acetate” by C Yufeng et al. published in Eur. Chem. Bull., 2012, 1(8), 336-337 reports a review of an a few synthetic methods of n-butyl acetate using different catalysts such as inorganic salt like (Ce(S2O8)2, FeNH4(SO4)2.12H2O, LaSO4/SiO2, KHSO4 and SnC14/C), HZSM-5, oxide (MoO3/SiO2), I2, heteropolyacid (H2(PW12O4O).nH2O), quaternary ammonium salt ionic liquid and nanometer ZnO. The review article discussed the maximum yield of n-butyl acetate was 98.5% using NH4Fe(SO4)2.12H2O as catalyst.
Transesterification of butanol with ethyl acetate can be carried out over homogeneous catalyst, but due to the well-known disadvantages of homogeneous catalysts are reinforced by environmental policies. But none of the prior art processes overcome of drawbacks such as need for specialized equipment, water wastage, adaptable to batch and continuous modes, catalyst leaching amongst.
Thus, it is technological challenge to develop ecofriendly and highly active heterogeneous catalytic process for butyl acetate synthesis. Very limited literature is available on transesterification of butanol with ethyl acetate over heterogeneous catalysts. Accordingly, the present invention develops a single step, environment friendly process for the preparation of butyl acetate from ethyl acetate using boron loaded zeolite catalyst in high yield.